I've found that clearing the exim queues of all frozen messages can often do wonders; while it's true that exim doesn't try to send frozen messages, it does have to read them to notice that they're frozen.
Here's what I found to remove all frozen messages:
Code:
# exiqgrep -z -i | xargs exim -Mrm
But unfortunately the exim packages distributed with DirectAdmin don't seem to include exiqgrep.
It's a simple script, included with default official exim source installs. I use it on our CentOS based systems, and I've put a copy here. I run it from /usr/sbin as that's where an exim install would normally put it (purists may want to put it in /usr/local/sbin). Be sure to chmod it 700 or 755, and to rename it to remove the .txt suffix.